CROTON-ON-HUDSON, N.Y. – Croton-Harmon school officials say the Sandy Hook Elementary School shooting resulted in an examination and change in security procedures at all three district schools.

"What Newtown did was bring to the attention, to everybody, a vulnerability that exists," Croton-Harmon Schools Superintendent Edward Fuhrman said at a Thursday evening meeting of the Board of Education. "The concern is the world is changing."

The district began examining security procedures before the mass shooting. The district hired security firm Altaris after an unresolved report of a stranger at Carrie E. Tompkins Elementary School.

In Tompkins Elementary School, classroom doors are now always locked and propped open. Teachers are required to carry classroom keys on their badges. Administrators hope this will make locking doors easier in the event of an emergency, as teachers need only to shut the door. Teachers also carry a small list of all students on their person.

All doors are locked, and all visitors must be let in through a buzzer system. Additionally, when visitors arrive they are asked why they're at the school, and if they're expected. If not, they are not let into the building, administrators said at Thursday's meeting. Visitors are asked to sign in and out.

Teacher assistants stand at entrances during pickup and drop-off times, and escort parents to the "welcome center," if they don't come in through the main entrance. The district is considering signs to inform delivery people that they may be asked for identification.

At the teachers' discretion, students are no longer allowed to call home for minor reasons.

At Pierre Van Cortlandt Middle School, all entrances are locked, including the main entrance. Students are not allowed to open side doors for visitors, and signs are posted on the inside of doors which say the same. Parents are escorted to classrooms for parent-teacher conferences. Administrators direct traffic during pickup and drop-off times. A teacher aide is at the main entrance when school starts.

Croton-Harmon High School has an open campus, which makes it the most difficult campus at which to limit foot traffic. All doors are locked, except the main entrance, after school starts. Administrators at Thursday's meeting said the open campus policy is unlikely to change, as the policy is closely tied to school identity. Altaris will be at the high school Monday to evaluate security procedures there.

Fuhrman said community members would soon be informed of "reunification posts," where parents would know where to pick up children in case of an emergency.

"Real change is not simple," said school board President Andrea Furey. "We take the safety of our children extremely seriously."